Vehicle for launching from a gas gun

ABSTRACT

A vehicle for launching from a gas gun having a housing; preferably incorporating a precessional attitude control system; and utilizing a flared base, fins, or active use of the attitude control system during passage through the atmosphere. Subtly canting the fins can produce desired spinning of the vehicle. The propulsion system can employ liquid, hybrid, or solid fuel. A removable aero-shell assists atmospheric flight with thermal protection being provided by anticipated ablation, an ablative aero-spike, or transpirational cooling. And a releasable sabot enhances the effectiveness of the launch.

This application is a continuation of PCT/US2010/050441, filed Sep. 27,2010 and entitled “Vehicle for Launching from a Gas Gun,” inventors JohnHunter, Harry Cartland, Philip Sluder, and Richard Twogood, which claimspriority to U.S. App. 61/277,544 and U.S. App. 61/277,543, each of whichwas filed Sep. 25, 2009. Each of the three preceding applications isincorporated by reference herein as if put forth in full below.

TECHNICAL FIELD

This invention relates to a vehicle such as a missile or rocket havingthe capability for self-propulsion but receiving its initialacceleration from being launched by a gas gun.

BACKGROUND ART

Projectiles launched from gas guns are known to use sabots.

The inventors of the present invention are, however, unaware of anymissiles launched from a gas gun which employ an aero-shell, technologyto protect the missile from heat generated during the missile's movementthrough the atmosphere, spinning and pulsed propulsive bursts from themissile to control the direction of the missile, oversized propellant oroxidizer tanks to be used for delivery of propellant or oxidizer, ormoving surfaces to induce lift during the portion of the missile'sflight within the atmosphere.

The present inventors have developed a means of delivering supplies toearth or lunar orbit in order to assist space exploration. The currentmethod of delivering propellant, food and other supplies to orbit iswith rocket delivery. Rocket delivery is extremely expensive with atypical cost of about $5,000 per lb of payload delivered. Therequirement for approximately 9 km/s delta V to attain earth orbit whencoupled with the rocket equation yields only a few percent payloadfraction for rocket delivery. Their method uses a hydrogen gas gun tofirst boost a rocket to high speed. This allows a smaller more efficientrocket to deliver the payload to orbit. The payload fractions obtainedare thereby much higher than obtained by a rocket alone. Their higherpayload fractions plus the re-usable hydrogen gas gun reduce the payloaddelivery cost by more than a factor of 10.

The present inventors have previously described using hydrogen gas gunsto deliver payloads to orbit in the following published articles:“Livermore Proposes Light Gas Gun For Launch of Small Payloads”,Aviation Week and Space Technology, Jul. 23, 1990, pp. 78-80; “ShootingRight For The Stars With One Gargantuan Gas Gun”, Smithsonian Magazine,January 1996, pp. 84-91; and “The Jules Verne Gun”, Popular Mechanics,December 1996, pp. 54-57.

DISCLOSURE OF INVENTION

The Vehicle of the present invention utilizes an aero-shell, technologyto protect the missile from heat generated during the missile's movementthrough the atmosphere; spinning and pulsed propulsive bursts from themissile to control the direction of the missile, in one embodiment;oversized propellant or oxidizer tanks to be used for delivery ofpropellant or oxidizer, in one embodiment; and moving surfaces to inducelift during the portion of the missile's flight within the atmosphere,in one embodiment.

The launch vehicle has the following objects and advantages:

-   1. It has a sabot as shown in FIG. 1 that allows a larger working    area for the hydrogen pressure. This gives the vehicle greater    velocity for a given hydrogen pressure.-   2. It has a sacrificial aero-spike at the nose to reduce the heat    transfer on the forward part of the vehicle. The aero-spike will    ablate several inches during atmospheric flight. The advantage is    the aero-shell fore-body is substantially away from the high speed    air stagnation point at the aero-spike tip and hence will not heat    and ablate excessively.-   3. It preferably spins about the long axis thereby averaging out    aerodynamic moments and heating. This reduces peak bending forces    and hot spots.-   4. It preferably has an Attitude Control System (ACS) that only    requires one nozzle. The ACS includes sensors; an intelligent    microprocessor-based controller; a small propellant tank; and a    single, rapidly responsive rocket motor as shown in FIGS. 2 and 4.    The single nozzle pulsing at right angles to the vehicle cause the    spinning vehicle to precess to the desired orientation. The    advantage is a much lower part count and weight than a traditional    ACS which usually has multiple nozzles.-   5. It preferably has propellant tanks that can carry both the    propellant and the payload. This is because the payload is often    rocket propellant such as LH₂, LOX or RP1, while the vehicle uses    the same propellant. This will reduce the part count and weight of    the vehicle.-   6. It preferably has a plug nozzle. The advantage is a much shorter,    compact nozzle than a conventional central nozzle. This will    increase ruggedness under the high G launch loads. It will also    allow for a more compact and lighter vehicle.-   7. It preferably has a centripetal fuel pump based on vehicle    rotation. The rapidly spinning vehicle can generate significant    hydrostatic propellant pressures at the periphery of the propellant    tanks. Propellant can then be fed through a pressure regulator to    the plug nozzle. The advantage is in eliminating a turbo-pump or    pressure bottle that is ordinarily used to pressurize the    propellant. This will save weight and reduce cost.-   8. It preferably has liquid propellant comprised of an oxidizer and    a fuel. One advantage is no in-bore detonations in the event of    vehicle break up in the launcher. Other advantages include higher    specific impulse as well as the ability to throttle thrust.-   9. It obtains a large amount of initial velocity from gun launch.    This reduces the amount of propellant needed and results in higher    payload fraction to orbit than conventional rocket delivery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the launch vehicle with sabot.

FIG. 2 shows the vehicle aero-shell.

FIG. 3 shows the rocket motor and payload.

FIG. 4 shows the axial plug nozzle as well as and ACS and its smallradially directed rocket nozzle.

FIG. 5 shows a close up of the plug nozzle and the ACS.

FIG. 6 shows the launch vehicle inside the gun before launch.

MODES FOR CARRYING OUT THE INVENTION

The launch vehicle, illustrated in FIGS. 1 through 6, has a sabot thatencloses the aero-shell and gives it an effectively larger area. Thesabot is preferably composed of at least two petals, even morepreferably of two to six petals, and most preferably of four petals. Thepetals are a composite or aluminum and fall off of the aero-shell whenthe vehicle emerges from the launcher and encounters aerodynamic forces.

The aero-shell preferably has a power law shape of the form r=AX^(P)where the exponent is 0.75, although other viable shapes such asbi-conic exist. The acceptable range of exponent is, though, between0.25 and 1.5, inclusive. The length to diameter ratio L/D is between 3and 20, exclusive of the endpoints. An L/D of 5 has about 4 times thedrag of an L/D of 10. The reason for excluding L/Ds greater than orequal to 20 is the fragility of long skinny objects at extreme speeds inair. Conversely, an L/D of 1, will be rugged but have unacceptably highdrag.

The aero-shell covers the housing of the vehicle without, of course,blocking the rocket motor nozzle, and is composed of carbon-phenolic orsimilar and has a wall thickness appropriate to the in-bore stresses itwill experience. (Carbon-phenolic is a name known by one of ordinaryskill in the field of thermal protection for aircraft and reentrybodies.) Inbore stresses are a result of base pressure, velocity, barrelstraightness, and vehicle/sabot material. Those of ordinary skill in theart who design vehicles, e.g., designers for the light gas gun at AEDCin Tennessee, use computer FEA (Finite Element Analysis) predictions todesign hypersonic gun-launched vehicles based on those properties. Inaddition to using computer programs to determine wall thickness, it isdesirable to take data from a large number of test launches to validateand augment the FEA results.

The fore-body is preferably capped with an ablative aero-spike asillustrated in FIG. 2, although other nose-protection schemes don't usean aero-spike but accept a certain level, such as 5 to 10 inches, ofnose ablation. And optionally the nose is cooled by transpiration,wherein a fluid such as water is forced through holes in the nose ofaero-shell and other areas where thermal protection is desirable. Theaero-spike is made of a rugged high Q* material like carbon-carbon oroak. It is approximately 1″ in diameter and 10 inches long. (Aero-spikelength varies depending on vehicle size and velocity. For the figuresgiven here the inventors have assumed a 1-meter diameter aero-shell anda velocity of 6 km/s).

Qstar refers to the heat of ablation of a material under extremely highheating rates consistent with orbital speeds. Carbon-Carbon is known tothose of ordinary skill in the field of thermal protection for re-entryvehicles. For example, Teflon, Carbon-Carbon, and oak are amongacceptable ablative TPS (Thermal Protection System) materials.Carbon-Carbon has a Qstar in excess of 5,000 Btu/lb or 1.2e7 joules/kg.PICA (Phenolic Impregnated Carbon Ablator) and PICA-X are recentacceptable coatings used by NASA and Space X.

Aero-spike dimensions and length can be computed by the use of ablationcodes such as Coyote and ABRES (ASCC86) at Sandia National Laboratories.Don Potter at SANDIA's Aeroscience and Compressible Fluid MechanicsDepartment, has run his shape changing ablation codes for the inventorsin the past to predict the shape of an ablated vehicle nose. This is astraightforward yet challenging piece of engineering. There will be sometrial and error. There are probably several hundred individuals ofordinary skill in the field at SANDIA, LLNL, Los Alamos, NASA, andassorted companies like SpaceX, Boeing and Lockheed who can perform thework. There will be some testing required in addition to thesimulations.

The aft section of the vehicle preferably has a flared base in order tomove the center of pressure rearward to increase stability. An ACS(Attitude Control System) nozzle, shown in FIGS. 2 and 4, is preferablynear the base in order to help provide stability during atmospherictransit. In addition, subtly canted (preferably less than five degreeswith reference to the longitudinal axis of the vehicle because of theextreme speeds, heating rates, and dynamic pressures experienced by thevehicle in the atmosphere) fins are optionally present near the base toprovide spin.

An aero-shell ejection charge, illustrated in FIG. 2, is located nearthe tip of the vehicle. Timing can be determined by an on-boardaccelerometer that determines when the vehicle has obtainedapproximately 60 to 100 km altitude or more. The first actuator is shownat the nose in order to push the motor and payload out of the hotaero-shell. There will be other actuators including exploding bolts andcutting charges required to sever internal structures to free the motorand payload from the aeroshell. These other actuators will be firedprior to the actuator on the nose which ejects the motor and payload.

When the vehicle is powered by a solid propellant, a cargo compartmentwill exist. This is also an option when the vehicle uses liquidpropellant.

More commonly, however, if liquid propellant powers the vehicle, thevehicle contains an oxidizer tank and a propellant tank, as illustratedin FIG. 3, with at least one tank being oversized to carry additionaloxidizer or additional propellant as cargo. Instead of, or in additionto, an oversized tank, a third tank optionally exists in order to carryliquid cargo other than an oxidizer or propellant, such as water orxenon.

A standard liquid propellant is most preferred, a hybrid fuel ispreferred, and solid fuel is the third in terms of priority ofpropellants. Hybrid rockets use a fuel such as acrylic, polyethylene orpolybutadiene and then flow a gaseous oxidizer like oxygen or nitrousoxide over the fuel surface. They are safer than ordinary solid motorsyet still throttleable via the oxidizer. Of course when liquidpropellant is utilized, there must be one or more valves to control thepropellant and oxidizer; and in a hybrid rocket there must be a valve tocontrol the oxidizer.

Attitude control of the vehicle is possible with a standard nozzle ormultiple standard nozzles; preferably, though, a rocket plug nozzle isutilized, as described below and as illustrated in FIGS. 4 and 5.

For either the primary motor or the attitude control system motor amanifold and igniter exist unless the propellant is hypergolic, in whichcase an igniter is unnecessary. In the case of the rocket plug nozzlethe manifold is located near the plug nozzle and regulates anddistributes the propellant which is pressurize preferably fromcentripetal force created by spinning the vehicle. The propellant can beextracted near the periphery where the pressure will be the greatest.

The propellant will be extracted at the maximum diameter for the tanks,which are preferably tapered. The centripetal force/pressure will begreatest there. (There may be some issue with spinning a liquid sincethis can lead to a “flat spin” due to dissipation; however, there arerealistic solutions, such as gelling or freezing the liquid orincorporating baffles.) The inventors prefer using the rapid spin topressurize the propellant as it is novel and should eliminate aturbopump or pressurization tank, which will produce significant weightand cost savings. A traditional approach is to use a turbopump, aninternal combustion engine pump, or a gas, usually helium, pressurant.Another novel method is to employ a heat sink that taps the aero-shellheat during egress and later transfers the heat to the propellant,thereby vaporizing and pressurizing it. The inventors still prefer thespinning liquid centripetal pump, even though it will requiresubstantial engineering and testing.

The ACS nozzle of FIG. 5 penetrates the aero-shell. After the aero-shellis discarded along with the exterior ACS nozzle, the interior ACS nozzleis exposed for maneuvers in the vacuum of space.

FIG. 5 shows the annular ACS monopropellant tank is located inward ofthe plug nozzle. FIG. 5 is a cutaway. As best seen in FIG. 4, the plugnozzle and the ACS tank are distributed over the full 360 degrees. Asshown in FIG. 5, the exhaust impinging on the ACS tank as shown can beproblematic. Preferably, the plug nozzle is directed inward, preferablysubstantially 20 degrees inward; and the inner part of the nozzleextends below the ACS tank.

The ACS is controlled by a microprocessor and sensor package (not shownsince these are traditional elements). The sensors include anaccelerometer, a GPS, a radio transmitter and receiver, a horizonsensor, and a payload integrity sensor. One of ordinary skill in the artwould understand control of the ACS system. This includes employees ofBall Aerospace, Boeing, Lockheed-Martin etc. who regularly maneuversatellites.) The sensor package preferably uses a combination of GPS andinertial guidance, plus active radio telemetry with the propellantstation. This is discussed more on page 3 of the vehicle patent. TheRussian's Progress resupply vehicle use an autonomous docking systemcomprised of the TsVM-101 digital flight computer plus the MBITS digitaltelemetry system. In 2007 DARPA also demonstrated autonomous dockingwith Orbital Express. DARPA used AVGS (Advanced Video Guidance System)to guide the docking.

The microprocessor controller is capable of repetitively pulsing thesmall rocket motor shown in FIG. 5.

The operation of the Gas Gun Launcher is as follows:

The launch facility first scans the area down range with radar andvisually to insure range safety.

The gun is cleaned and prepared to accept the vehicle.

Next the launch vehicle is loaded with propellant and payload andinserted down the launch tube from the muzzle until it seats near thepump tube (and the sliding seal in the OBL) as in FIG. 6. If thepropellant is cryogenic, then propellant may be vented and topped off asneeded by thin tubing penetrations that reach the vehicle from outsidethe launch tube.

From this point on the system is operated remotely.

A vacuum of a few Torr is pulled separately in both the launch tube andpump tube. Care must be taken to maintain lower pressure behind theprojectile so that it does not get pushed toward the muzzle. The gun isenergized and prepared for launch.

The tracking radars are notified and the gun is fired. The vehicle isaccelerated down the launch tube to high speed and pushes a small amountof shocked air in front like a snowplow. The shocked air impacts adiaphragm, preferably composed of MYLAR, at the muzzle and blows itoutward allowing the vehicle to exit the gun unscathed.

The vehicle emerges from the muffler and the sabot petals are liftedaway from the aero-shell by aerodynamic forces. The petals burn, becauseof air friction due to the high speed of the vehicle, while airborne andland within a few km of the muffler. The vehicle is either spinning onexiting the launch tube or spins up in the atmosphere due to the subtlycanted fins. Vehicle orientation changes are made if needed by drivinggyroscopic precession. The angular precession rate is given by:Angular Rate=Torque/Angular momentum  (Eqn. 2)(Here torque is applied at right angles to the angular momentum axis.See “The Feynman Lectures on Physics” Vol. 1 Chapter 20, p. 6, Eqn.20.15.)

The preferred ACS has a major novel feature in that it achievesorientation via stroboscopically applying thrust at right angle to thespin axis of the vehicle in accordance with Eqn. 2 above. This isimportant and different. Alternatively we can use conventional ACSthrust maneuvers which don't require a spinning vehicle, but they dorequire more thrusters. (Conventionally 2 thrusters for pitch and 2 foryaw located near the nose, as well as 2 for roll located near the centerof mass.)

Spinning the vehicle can be performed several ways. The fins will bevery small canted protuberances on the aft section. They will not stickout more than say 5% of the vehicle diameter, and are expected to have acant angle of 1 degree<theta<5 degrees. Their length can be 5-100% ofthe vehicle diameter. Optionally, grooves similarly oriented on thesurface of the vehicle can be employed. And alternatively the inventorsbelieve a practical technique is pre-spinning the vehicle in thelauncher prior to launch by spinning the section of launch tubecontaining the vehicle is. The other option is to hone the barrelpreferentially in one direction. Of the three techniques, pre-spinningthe vehicle is likely the most precise. The fin option however, has aside benefit in that it will stabilize the projectile bothgyroscopically as well as by moving the center of pressure aft of thecenter of gravity. All of these methods can be accomplished by oneskilled in the art; however, significant engineering and testing will berequired.

Eqn. 2 is more transparent here: Dtheta=Dt*Force*(length to center ofmass)/Angular momentum. Force being that applied by the ACS singlethruster as it pulses. Sensors determine the orientation of the vehicleso that the microprocessor, or controller, can issue commands to achievethe desired orientation. Naturally there are other sensors on-board todetermine where the vehicle is relative to the depot as well as therelative velocity etc. There are also the usual payload integritysensors etc.

As the vehicle ascends through the atmosphere, the aero-spike seesmaximum heating and will ablate substantially. The rest of theaero-shell should remain largely undisturbed although the minimal finsmay also get ablated somewhat. After attaining approximately 60 to 100km altitude the aero-shell will be ejected exposing the rocket motor andpayload. Shortly thereafter, the rocket is ignited and burns forapproximately 100 seconds as it nears the orbital depot. The spinningrocket causes significant centripetal propellant pressure thereby, inthe preferred embodiment, circumventing the need for a tankpressurization device or a turbo-pump. With the sensors providing inputto the microprocessor, or controller, the ACS knows the vehiclelocation, velocity, and orientation during and after the rocket burn. Itcontinues to orient the spinning rocket/payload assembly as theyapproach the depot. The ACS is also in communication with the depot asneeded in order to perform final maneuvers.

Upon arriving near the depot a robotic tug fields the rocket/payloadassembly. It determines payload integrity and then delivers therocket/payload assembly to the propellant depot where the propellant issiphoned off. The now empty payload compartment and the rocket assemblyare stored for future disposal or recycling.

Alternatives or options in addition to those discussed above are asfollows:

The vehicle may be spun up while in the launcher by having a motorspinning the section of launch tube where the vehicle is seated whilemaintaining a good seal. Another method is to hone the launch tube in aparticular direction (say clockwise). This has been known to impart spinto high speed projectiles. Note that at the speeds under considerationby the inventors (greater than 3 km/s) conventional rifling does notsurvive the shot.

The vehicle may have movable features that induce lift duringatmospheric traversal in order to access different inclination orbits.This is similar to MARV technology for re-entry vehicles.

The liquid propellant may be pressurized via a conventional heliumpressure vessel, a turbo-pump, or an internal combustion pump.

The rocket motor may have multiple stages.

The rocket motor may have a conventional central nozzle to provide axialthrust.

The vehicle may use a conventional attitude control system incorporatingmultiple nozzles.

The vehicle may use solid or hybrid propellant rockets in one or morestages.

The vehicle may have autonomous docking with the depot or satellite.

As used herein, the term “substantially” indicates that one skilled inthe art would consider the value modified by such terms to be withinacceptable limits for the stated value. Also as used herein the term“preferable” or “preferably” means that a specified element or techniqueis more acceptable than another but not that such specified element ortechnique is a necessity.

And non-essential features may be utilized in any and all practicalcombinations.

INDUSTRIAL APPLICABILITY

The way in which the Vehicle for Launching from Gas Gun is capable ofexploitation in industry and the way in which the Vehicle for Launchingfrom Gas Gun can be made and used are obvious from the description andthe nature of the Retractable Hose Extension for a Vacuum.

The invention claimed is:
 1. A vehicle for launching from a gas gun,which comprises: an aero-shell configured to be jettisoned duringflight; within an area defined by said aero-shell, a rocket propulsionsystem; wherein at least one of the aero-shell and a vehicle body withinsaid aero-shell is configured to induce spin in the vehicle duringflight; and said vehicle further comprising a releasable sabot enclosingat least a portion of said aero-shell.
 2. A vehicle according to claim 1and further comprising a payload within the vehicle body covered by saidaero-shell.
 3. A vehicle according to claim 2 wherein the payloadcomprises at least one selected from fuel and oxidizer.
 4. A vehicleaccording to claim 3 wherein at least one of the fuel and the oxidizeris contained in an oversize tank.
 5. A vehicle according to claim 2wherein the payload comprises cargo separate from the fuel and theoxidizer.
 6. A vehicle according to claim 5 wherein the cargo resideswithin a chamber within the body.
 7. A vehicle according to claim 2wherein the aero-shell has an aerospike positioned at a pointed end ofsaid aero-shell.
 8. A vehicle according to claim 2 with the vehicle bodyfurther comprising an attitude control system.
 9. A vehicle according toclaim 8 wherein the attitude control system comprises a rocket nozzlepositioned at a side of the vehicle in a position to apply thrustperpendicular to a spin axis of the vehicle.
 10. A vehicle according toclaim 9 wherein the rocket nozzle is configured to stroboscopicallyapply thrust.
 11. A vehicle according to claim 8 wherein the attitudecontrol system comprises roll thrusters.
 12. A vehicle according toclaim 2 and further comprising a centripetal pump in fluid communicationwith a propellant tank of the rocket propulsion system.
 13. A vehicleaccording to claim 12 and said vehicle body further comprising anattitude control system.
 14. A vehicle according to claim 13 wherein theattitude control system comprises a rocket nozzle positioned at a sideof the vehicle in a position to apply thrust perpendicular to a spinaxis of the vehicle.
 15. A vehicle according to claim 14 wherein therocket nozzle is configured to stroboscopically apply thrust.
 16. Avehicle according to claim 2 wherein the rocket propulsion systemcomprises a single plug nozzle.
 17. A vehicle according to claim 16wherein the plug nozzle is in fluid communication with a centripetalpump of the rocket propulsion system.
 18. A vehicle according to claim 1and said vehicle body further comprising an attitude control system. 19.A vehicle according to claim 18 wherein the attitude control systemcomprises a rocket nozzle positioned at a side of the vehicle in aposition to apply thrust perpendicular to a spin axis of the vehicle.20. A vehicle according to claim 19 wherein the rocket nozzle isconfigured to stroboscopically apply thrust.
 21. A vehicle according toclaim 1 and further comprising a centripetal pump in fluid communicationwith a propellant tank of the rocket propulsion system.
 22. A vehicleaccording to claim 1 wherein the aero shell has at least one of cantedfins and grooves.
 23. A vehicle according to claim 1 wherein the vehiclebody has at least one of canted fins and grooves.
 24. A vehicle and gasgun in combination, comprising (1) said gas gun, wherein the gas gun hasa launch tube adapted to impart spin to the vehicle and (2) saidvehicle, wherein the vehicle comprises an aero-shell configured to bejettisoned during flight; within an area defined by said aero-shell, arocket propulsion system; and said vehicle further comprising areleasable sabot enclosing at least a portion of said aero-shell. 25.The vehicle and gas gun of claim 24, wherein the launch tube adapted toimpart spin is honed in one direction to impart spin to the vehicleduring launch.
 26. The vehicle and gas gun of claim 24, wherein the gasgun adapted to impart spin to the vehicle has a section of said launchtube configured to spin in order to impart spin to the vehicle duringlaunch.